Welcome to
FUN WITH TUBES.

This is a noncommercial site
operated by Max Robinson and
dedicated to passing on and preserving
knowledge of vacuum tube circuits and techniques.

Keep the electrons flowing and the tubes glowing.


JOIN NOW!

Join the Fun with Tubes discussion group.
Now all of you who have been exchanging email
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other directly. To subscribe send an email to
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The people who run the website EE Web have
interviewed me and written a very
nice article. Here is the link.
EE Web article.


An Observation.

If I worked on radios the same way doctors worked on people when ever a capacitor, resistor, or tube, failed I would just take it out and throw it away. Yet the radio would be expected to work as well as when it was new. So far I am down my tonsils, adenoids, about one and a half feet of large intestine, and a gall bladder. My power output is down and my distortion percentage is up.


Fun With Tubes now has a sister site.
It's called Fun With Tran-sisters.
If you would like to tinker with electronics
But you would rather not poke around among
High voltages, check it out.



New!

Speaker Impedance
Did you know it isn't constant?
Characterizing Transformers
and Interpreting Lead Colors.
The Wise Linearized Williamson Circuit.
Even this classic can be improved upon.
Harman-Kardon A-300
New information has been added
including distortion measurements.
Hotel Radio.
Have you ever seen one like this?
Design Stable
Feedback Loops

Resistor's Behavior
at MF, HF, and VHF.

A resistor may not
always be a resistor.
Transmission Lines and SWR
Some of what's on this page
may surprise long time hams.
Tube Cross-reference and Selection Guide.
Here are several tone control circuits with frequency
response curves. Practical Tone Control Circuits.


What do I need to have fun with tubes?
Click here for the answer.

The Basics of Electricity and Electronics.
DC Circuits: Series Circuits, Parallel Circuits, Ohms Law, and Scientific Notation.
AC Circuits: RC, RL, and RLC Networks, Filters.
Vacuum Diodes: Tubes with two elements.
Vacuum Triodes: Adding a grid to the diode.
Tubes with 2, 3, and 5 grids.
Amplitude Modulation (AM), Single Side-band (SSB), and Frequency Modulation (FM)
What is ground? One of the Most Misunderstood Concepts in Electricity.
Transmission Lines and Standing Wave Ratio (SWR): Another Misunderstood Concept.
Test Instruments.
How they work and how to use them.
Grid Dip Meter (GDM) / Grid Dip Oscillator (GDO).
The Neglected Q Meter.
How To Do It.
Restoring Electrolytic Capacitors that Appear to be Dead.
Testing Capacitors: Do You Really Know How?
Characterizing Transformers and Interpreting Lead Colors
Reading Resistor and Capacitor Color Codes
Soldering and Unsoldering
Eliminating Ground Loops
Links to Pages on Designing and Building Speakers
Tips From Mac's Workbench
Construction Projects
Granted, some of the projects below are silicon based.
These are test equipment and in this application, whether
we like it or not, silicon is more stable, easier to build,
smaller, lighter, and performs better, than tubes.
Inexpensive Line Voltage Changer
Low Resistance Adapter for a Digital Multimeter
Using the Low Resistance adapter to characterize Unmarked Power Transformers
Filter Choke Analyzer: Test Filter Chokes Under Current Load.
8 Simple Power Supplies For Your Workbench.
Power Supply & Amplifier: Complex but Very Useful.
4 Ways to Breadboard: Only One of them is Any Good.
An IC Socket for Tubes: Not Nearly as Good as it Seemed.
The Best Breadboard: Soldering Doesn't Take Much Longer and is More Reliable.
A Load Box for Testing Power Supplies
Making IF Transformers. It's harder than I thought
Modifying a Heath IG-18 Audio Generator For Ultra Low Distortion.
PLL Frequency Control For AM Band Receivers. Know Where You Are.
Radio and Detector Circuits.
How AM Radio Works: A Simple Description.
How FM and FM Stereo Works
Winding Coils: To Wind or to Buy. Only You Can Answer That Question.
Build a Crystal Set
Build De Forest's Audion: That's Right, You Can Build His First Version of the Audion.
Grid Leak Detector: Needs an Amplifier.
Plate Detector: Needs an Amplifier.
Infinite Impedance Detector: Needs an Amplifier.
Regenerative Detector: Needs an Amplifier.
TRF Receiver: Needs an Amplifier.
Simple Superhet Receiver: Discusses Principles of Mixing and Image Frequencies.
3-Tube Superhet: Needs an Amplifier.
4-Tube Superhet: Needs an Amplifier.
5-Tube Superhet: No Coil Winding, Complete.
The All American Five: There Were Millions Made.
Introduction and Power Supply
The Converter
The Intermediate Frequency Amplifier
The Detector
The Audio Section
Cautions, Precautions, and Troubleshooting
Audio Amplifiers: How They Work
Power and Output Transformers: The Basics.
A Basic Power Supply: Found in the Newcomb D10.
A Technical Discussion of Power Supplies: Not For the Faint of Heart.
Resistance Coupled Amplifier, A Basic Building Block
Magnetic Phono Preamp: With Two Examples.
Volume and Loudness Controls; What the manufacturers don't want you to know.
Tone Controls: From Simple to Complex.
Balance Controls: The Good, the Bad, and the Useless.
Phase Inverters, Split Load Phase Inverters, and Drivers
Push-Pull Outputs
Overall Feedback, Pros and Cons
The FTC and Amplifier Power. Caveat Emptor.
Audio Amplifier Design.
How Much Power is Enough? It Depends.
Speaker Impedance: Did you know it isn't constant?
A Low Distortion Gain Block: Gain from 6.7 to 34, THD less than 0.060%.
How Does Removing the Cathode Bypass Capacitor Effect Distortion.
Practical Tone Controls: Passive and Active.
Phase Inverters and Drivers: The Heart of an Amplifier
The Wise Linearized Williamson Circuit.
An Amplifier Test Bed: Low THD Driver, Full Metering, & Regulated G2 Voltage.
Experiments with Triode Power Amplifier Circuits.
Designing an Amplifier with Feedback. A Downloadable Program Helps.
How To Design and Optimize Feedback Loops For Best Performance.
Optimizing Feedback Loops, a different point of View. Tim E. Smith.
An Amplifier Smorgasbord: Take Your Choice.
50 Watt Monoblock Amplifier: 6L6 GC.
Ultra Linear Monoblock: 6L6 GC.
Triode Monoblock: 6L6 GC.
An EL34 Ultra Linear 50 Watt/Channel Amplifier.
A Unique Circuit Circlotron Amplifier: Probably Not Worth the Complexity.
Contest Winning Amplifier: Results of the 2012 Amplifier Contest.
Story of the Original Koss Headphones: Leads Into the Next Project.
A Dedicated Headphone Amplifier
The 70 Volt Line Amplifier
Photo Gallery
The Hotel Radio: No Longer a Mystery.
Project Pictures Sent to me by Viewers of this Page.
Schematics of Viewer's Projects.
Tour My Kilowatt AM/SSB Ham Station
Tour My Old Tube hi-fi and Stereo Systems.
The Lawnmower House, The Teddybear Cottage, and My Woodshop.
A New Workbench and Other Revisions to my Electronics Shop.
It Isn't Finished. Work on the Electronics Shop continues.
Operating Instructions
Silvertone Wire Recorder/Phonograph/Radio
MaxCAD Drawing Program Instruction Manual
Restoration Projects
1937 Philco Radio: This Radio Needs a Battery Eliminator to Work.
Heathkit Power Supply: The Fault Was a Most Peculiar Tube.
Harman-Kardon A-300: A Basket Case From eBay Plays Again.
Atwater-Kent Model 20: Restoring a 93 Year Old Radio Isn't Easy.
Useful Information
Verifying My Test Equipment: Making Accurate Measurements is not Easy.
Resistor's Behavior At HF and VHF. When is a Resistor Not a Resistor?
Tube Cross-reference and Selection Guide
Catalogs of Discontinued Parts
Useful and Interesting Links to Other Sites.
Free Programs You Can Download
Other things you can download.
Rants.
Textbook, Electronics for Non-Engineers
Textbook, Troubleshooting Techniques.
E-mail me


Do you like music? I also write songs which are arranged and mixed
so you can understand the words, and the lyrics are worth listening to.
Take a peak into my right brain. Visit Max's Music Place. Click here.


Email Tube Man.  SHA ZAM!
Everything you always wanted to know about
vacuum tubes but didn't know who to ask.

Ask Tube Man.

Would you like to tinker around with tubes but don't know what to do? Want to fix up that radio that belonged to your great-grandfather but don't know where to start? Are you experienced in working with tubes but you just came across a problem which has you stumped? Tube Man knows all and tells all. Just click on the super hero's picture to email a question to him. See questions submitted to Tube Man and his answers.


Who and What.

This web site is owned and operated, as a hobby, by Max Robinson. As time goes by I will post tutorials on the fundamentals of electricity and electronics, interesting circuits you can build with vacuum tubes and op amps, and I will share some of my experiences restoring antique radios and early electric phonographs.

I have a master's degree in electrical engineering from the University of Florida 1966. My early EE classes covered vacuum tubes so I know what I am talking about and doing. If you have any questions or suggestions feel free to email me.


If I Don't Answer...

I scrupulously answer all emails sent to me. If you send me one and you don't hear from me in a reasonable amount of time maybe something went wrong.

On a number of occasions I have received emails from people seeming to be asking legitimate questions. When I attempt to answer them I get back one of those "Mail System Error" messages saying that there is no such address or my email address has been blocked by the sender. Some anti spamming programs are quite strict and maybe you forgot to enter my address as "allowed". Check your anti spam list to be sure my reply will be given to you instead of being bounced back to me.

On the other hand maybe this is someone's idea of juvenile fun. No doubt the people who have done this (you know who you are) think this is very funny. To me it's just a minor annoyance. Even though it's a small thing I could do without it. Just because you're not having fun don't spoil it for the rest of us.


My Favorite things.
  • Old Country Music
  • Old Rock-n-Roll
  • Folk Music
  • Classical Music
  • Old Radios
  • Old Records
  • Old Record players
    Gramophones, Victrolas, etc.
  • Young Women (Only kidding Sue.
  • One particular woman (age, I'm not telling).


Thank you for visiting my page at Angelfire.
Please come back and visit again!

This site begun March 14, 2001

This page last updated May 7, 2012.


Web ring has been removed because it was hijacking browsers away from this site into the ring. The ring has been rung.